The field of the invention is controllers for industrial power supply systems.
High power inverting type power supplies are used for such typical industrial applications as induction heating, corona treating, and cap sealing. The inverting power supply system first rectifies the incoming AC supply voltage to Direct Current (DC). Switching elements, for example silicon controlled rectifiers (SCR's), are then used to switch energy from the DC bus into a tank circuit which is tuned to a resonant frequency, usually much higher than the input line frequency.
The control systems used for controlling such inverter power supplies provide basic control over the operating power level of the inverter power supply and some limited instrumentation to indicate basic operational quantities such as, for example, the input voltage, the output voltage, the output frequency, etc. Only a few of such quantities are displayed since each one requires a dedicated meter. To display a large number of operational quantities requires many dedicated meters, which increases the cost and panel space required for the system. When a problem develops with the inverter power supplies, maintenance must be performed on site due to their large size. This usually involves travel by a technician from the power supply manufacturer to the site of the failed power supply. Then, test equipment must be connected to the power supply to obtain diagnostic signals to identify the cause of the malfunction. One of the most useful diagnostic signals is the switching waveform signal produced across the switching elements. The most common practice is to connect an oscilloscope to the switching waveform signal so that timing measurements may be obtained.
Other points within the power supply too may need to be monitored, and other tests may need to be performed to determine the cause of the malfunction. For example, the technician may need to test the switching elements or SCR's, to determine if any of them are shorted. This task also requires connection of special test equipment to the power supply.
In short, diagnosing a faulty power supply has been a time consuming task requiring on site maintenance with sophisticated test equipment.